The role of an RNA primer in DNA chain initiation will be determined in L929 (mouse), 3T3 (mouse), and CVL (African green monkey) cell lines and the kinetics of DNA chain initiation investigated during the S phase in synchronized cells. The effects of cytocidal (reo, Mengo, Newcastle disease) and transforming (SV40) viruses on cellular DNA chain initiation and elongation will be measured. The effects of puromycin, cycloheximide, and 5,6-dichloro-1-Beta-D- ribofuranosylbenzimidazole (DRB) will also be determined. The SV40 DNA-protein complex will be investigated with respect to the role of newly synthesized histones in SV40 DNA replication; presence of non-histone chromosomal proteins; significance of protein acetylation, phosphorylation and methylation; and transforming activity. Host cell induction by SV40 infection will be examined to define virus-induced changes in non-histone nuclear proteins; to determine whether differences in cell susceptibility to transformation are related to demonstrable differences in their chromatin; and to determine the mechanism whereby cellular DNA synthesis is induced. The site of integration of SV40 genome in the host cell chromosome will be investigated with reference to repetitive sequences in the chromosomal DNA. The development of the P32 mRNA suicide procedure using interferon as a model will be completed and evidence sought for a putative interferon repressor mRNA. The mechanism of the selective action of 5,6-dichloro-l- Beta-D-ribofuranosylbenzimidazole on RNA transcription will be determined.